1. Field of the Invention
The present invention pertains to methods and apparatus for the determination of functional capability of bodies. More particularly the present invention relates to systems and techniques for quantitatively measuring the range of movement of which subjects, including human subjects, are capable, as well as the extent to which such subjects are capable of functioning at various attitudes. The present invention finds particular application to the measurement of human body movements and performance potential, including reach parameters and task-performing capabilities, the accumulation of such data and the presentation of such information for interfacing with design information characteristic of various environments. The anthropometric data acquisition available by means of the present invention may be utilized to accommodate and improve the interface between human subjects and various machines and work places including, for example, cockpits and cabins of spacecraft and other such confining and demanding environments.
2. Description of Prior Art
It is generally advantageous to improve the interface between man and his environment in various settings, and particularly work places where a subject or operator is required to perform various tasks. In some cases, it is critical to the comfort and safety of the human operator, as well as the efficiency of performance of the man/machine combination, that the work place be complementary to the performance capability of the operator. Since human body designs are generally fixed, to achieve a proper accommodation between man and machine the design of machines and work spaces may be altered where necessary. To determine environment design requirements to achieve a proper accommodation, it is first necessary to acquire human anthropometric and kinesimetric data in physical terms that may be applied to such machine and environment design. To characterize motion of human body segments in physical terms requires the essentially continuous measurement without mechanical interference of location in three dimensions, velocity, acceleration and force exertion of selected body points.
The description of the motion of the human body has previously been a tedious, expensive and time consuming procedure carried out usually manually, and has never been complete. Further, such measurements have never combined the two essentials of muscle activity, namely, motion and force. The usual procedure has been to measure a sample population of subjects for some particular aspect of motion of interest. In some cases, particularly where complex tasks are required, a mock-up of a proposed design is obtained and a representative sample of the prospective user population is placed in the mock-up to go through the required interface tasks.
A variety of techniques have been developed to attempt to measure one aspect or another of human activity. Generally these techniques require various degrees of manual data reduction to obtain quantitative results. Chronophotography techniques are known for motion study. However, while such techniques can be extended to three dimensions with the use of stereo cameras, such an approach is best limited to a single action, and requires extensive manual data reduction.
Various mechanical devices, including cable or rod arrangements, have been utilized to track an anatomical point and record its path within limitations, such as those defined by mechanical interference. I have previously devised a method of continuously registering the angle of a goniometer to allow it to continuously follow varying limb angles.
Various sonic, ultrasonic and electromagnetic radiators have been used to track points. Multiple receivers may be utilized, and the path of a radiator determined by the phase differences between the signals detected by the several receivers.
Video cameras have been used to record space location and motion patterns. The cameras detect light from reflective strips on dark-suited subjects, or from light sources including infrared light emitting diodes attached to various parts of the subject. Computer software has been used to analyze data from optical sensors. A computer approach has also been used to generate a synthetic man model based on static measurements from individuals. However, such a system is complex and expensive, and its accuracy and reliability are limited by available knowledge of the human body as a mechanical device.
Force and torque measurements have been made using various ergometers. A known cable tension arrangement allows only a static isometric determination of force at a single point. An isometric system using a fixed force, provided usually by weights, could be moved through a range of motion. Such systems, however, are limited to the maximum weight which can be moved at the "weakest" point of the range of motion. An improved isokinetic ergometer allows continuous measurement over a range of motion and torque, and over a range of speeds from a static, or isotonic, configuration to the maximum speed of which a body is capable.
A prior system combining force and position studies was directed to torques effected at human joints driven by external forces. Body limibs were rigidly attached to goniometers and driven through arcs with the resisting forces being measured.
Prior kinesimetric techniques have been characterized by the very limited amount and special nature of the data gathered as well as considerable time and expense needed to gather the data. Such known systems have not acquired complete data, that is, with force measurements combined with motion measurements including position, velocity and acceleration. Nor has such information been stored or displayed in a practical format utilizing engineering quantities.
Quality of the man/machine interface frequently determines performance of the man/machine unit, which often overrides performance of the machine design or the ability of the operator. This interface becomes increasingly important with machines of greater complexity and higher performance, particularly in the space program where machines and men are often operated beyond customary performance limits. Operations in a space environment are also complicated by variations in gravity, weightlessness, and alterations in size and shape of human bodies due to weightlessness.
An automatic video goniometer has been developed for the measurement of active body angles. The video goniometer includes a video camera, a master control with a microprocessor and a standard typewriter/terminal. A series of jigs containing coded point sources of illumination are attached to a movable body segment. The body segment is placed at one extreme of motion and its axis angle is measured either with respect to a local vertical or to a second reference axis. Measurement of the reference points on the video raster is effected automatically. Measurement of the segment axis angle at its other extreme of motion is similarly made. The miroprocessor calculates and presents the angular value.
Further aspects and details of advances in the field of anthropometry are discussed in "Measurement and Control of Human Movement", a collection of presentations by H. J. Woltring published in the Netherlands.